the national system. From the state line northward, M-10 was included as a part of US 24 and US 25. At Detroit, M-10 was used as a part of US 10. North of Grayling, M-14 was redesignated as a part of US 27. M-12 was used for US 2. The Michigan State Highway Department (MSHD) rerouted US 2 in 1933 between Rogers Park and Sault Ste. Marie. The new routing followed Mackinac Trail instead of turning east to Cedarville and north to Sault Ste. Marie; the former routing was given the M-121 designation. Turnpikes and freeways By 1945, a divided highway designated Alternate US 24 (US 24A) was opened from the state line north to Erie. After World War II, the MSHD planned to convert several highways in the state to freeways. In planning maps from 1947, the modern I-75 corridor was included in the system that later became the Interstate Highway System. It was also included in the General Location of National System of Interstate Highways Including All Additional Routes at Urban Areas Designated in September 1955 that was released in 1955 as the federal government readied plans for the freeway system. The Michigan Turnpike Authority (MTA), an agency which was created in 1951, proposed the construction of a toll freeway to run north–south in the state. The original termini for the turnpike were Bridgeport and Rockwood. The state highway commissioner at the time, Charles Ziegler, distrusted a separate agency dealing with statewide road building at the time, and he worked to stall progress on any proposed turnpikes. Ziegler, who had a seat on the MTA board, publicly sparred with authority chairman George Higgins, even announcing that the MSHD would build a parallel freeway that would "reduce tolls on the turnpike 40 to 50 percent" according to consultants. Trucking interests in the state also opposed the projects, preferring a moderate gas tax increase over any tolls. Detroit denied the MTA permission to route a turnpike through the city over issues related to the River Rouge, Rouge Park and access across the right-of-way. After a lawsuit by City of Dearborn, the legislation creating the authority was upheld by the Michigan Supreme Court in 1955, and the authority was allowed to sell bonds for its Bridgeport–Rockwood and Detroit–Chicago toll roads. The original planning maps plotted the first turnpike to the west of Detroit, running near US 24 (Telegraph Road). This route